Great Falls of the Potomac

According to a new study conducted by geologists at the University of Vermont, it was roughly 35,000 years ago that the Potomac River first began carving out the Great Falls of the Potomac. By analyzing a rare isotope formed by cosmic rays colliding with rocks and sediments on Earth's surface, researchers were able to gauge when and how quickly the Potomac River abandoned its ancient bed and cut through bedrock to form the terraces where people climb and hike today. Situated about 24 km (15 miles) west of Washington, D.C., Great Falls is a 3-square-kilometer (800-acre) park providing scenic views to hundreds of thousands of visitors every year. The site is particularly popular among hikers, climbers, and kayakers.